1. Technical Field
This invention relates generally to the production of plural sets of collated copies or prints (collectively referred to herein as "reproductions") from multiple-page original documents, and more particularly to the production of such sets of collated reproductions using digital reproduction apparatus with a collating buffer memory of limited page capacity.
2. Background Art
It is generally known to provide optical copiers with a recirculating document feeder having a hopper into which a multiple-page original document can be loaded for presentation seriatim to a platen. At the platen, one copy is made of each page before the page is returned to the feeder hopper. When all pages have been copied, a set of collated copies is presented. Plural sets of collated copies can be produced by repeating the process as often as needed.
Recently, digital copiers have been proposed in which each page of a hard-copy original is scanned to produce electrical signals representative of the image content of the originals. Digital printers operate on similar electrical signals derived from computers. In this description, the term "original document" is meant to refer to documents to be reproduced, whether in hard-copy or electronic form. The signals are stored in a multiple-page electronic buffer memory having addressable regions. The electrical signals of individual pages are selectively retrieved from the buffer memory in a scheduled order and presented to a writer such that images of the pages are produced on stacked receiver sheets to form a set of collated copies with pages properly sequenced. Additional sets of collated copies can be produced without re-scanning the original document merely by repeatedly retrieving the electrical signals in proper sequence.
Digital copiers and printers such as those described have a predetermined amount of available buffer memory. If the original document exceeds the capacity of the buffer memory, plural sets of collated copies from multiple-page original documents cannot be produced without "batching." Batching involves first reading into buffer memory the image data from a first sub-group of pages of the original document, producing as many sub-sets of collated copies of those pages as desired, reading the image data from a second sub-group of pages of the original document into the buffer memory, producing as many sub-sets of collated copies of those second sub-group pages as desired, and so forth, until all the pages of the original document have been reproduced. The operator assembles the sub-sets to form complete sets of collated copies.
Manual or automatic assembly of batched sub-sets of collated copies is cumbersome, but would generally be acceptable. However, there are certain operational modes in which batching would present an even greater disadvantage. Many copiers are provided with finishers having operations that require the entire set of collated copies. For example, stapling and folding functions cannot be effected unless the entire set is available; something that would not happen in a batch mode.